1. Field of Invention
The present invention relates to a semiconductor device, and more generally to a MEMS diaphragm.
2. Description of Related Art
Micro-electromechanical system (MEMS) devices are mini-electromechanical devices, and the manufacturing technology thereof is similar to that of integrated circuits. With the rapid development of the electronic industry and the manufacturing technology of integrated circuits, the MEMS devices fabricated based on the MEMS technology are varied and include tiny electromechanical devices such as accelerometers, switches, capacitors, sensors and diaphragms. The MEMS devices are widely applicable to electronic products due to the advantages of light weight, small size and excellent quality. For example, the MEMS diaphragms fabricated based on the MEMS technology have become the mainstream in the mini-microphone market, and are applicable to cell phones, digital cameras, cordless headsets, laptops, hearing aids and electronic ears.
Generally speaking, a MEMS diaphragm includes a bottom electrode, a top electrode partially suspended above the bottom electrode, and a dielectric layer between the top and bottom electrodes. In the process of fabricating the MEMS diaphragm, after a bottom electrode, a dielectric material layer and a top electrode having openings are sequentially formed on a substrate, a portion of the dielectric material layer is removed by the etchant such as hydrofluoric acid through the openings in the top electrode, so that a dielectric layer is formed between the top and bottom electrodes. Accordingly, the top electrode is suspended above the bottom electrode and having the vibration property. For example, when the top electrode is vibrated by sound waves, the capacitance between the top and bottom electrodes is changed, and the sound waves are converted to electric signals by the MEMS diaphragm.
However, during the step of removing the portion of the dielectric material layer, the etchant may over-etch the dielectric material layer and even damage the electronic devices around the MEMS diaphragm. Therefore, the device characteristics of the MEMS diaphragms and electronic devices are affected.